Pulse generator



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Oct. 28, 1952 w. P. BooTHRoYD 2,616,047

PULSE GENERATOR Filed March 13. 1948 s sheets-Sheet s 7U FIG. 7.'

. INVENTOR. Wma/1K A 50m/@0m Y F/G. Z

Oct. 28, 1952 w. P. BooTHRoYD 2,616,047

PULSE GENERATOR Filed March l5. 194B 6 Sheets-Sheet 4 W. P. BOOTH ROYD PULSE GENERATOR Oct. 28, 1952 6 Sheets-Sheet 5 Filed March 13. 1948 IN V EN TOR.

Patented Oct. 28, 1952 UNITED STATES @FI-wifi to Philco Corporation, Philaueipiiiagjrag? 'sepi- This invention relates to generators vof generally triangular electrical'pulSeS. While this invention is particularly applicable to multiplex 'signal transmitting vand 'receiying systems', its' capability ofl generating accurately spaced pulses of definite shape makes it applicable to I,timing systenis'in general. Because of its pecular'fdsiraility as a por-tion o f time multiplex systems'it'vvillbe de-. scribed as cons'tructedho application to such a System' .The principal vobject yof this. invention is to prvide'a generator? of precisely spaced' .pulses of constant Wave ,shapel Airthefobject of this invention is to providefsuh v'a pulse-generator which is readily 'controllable andi which has a series. of .output terminals' which Vare energizedsucess'ivelyin .a precisely .timed sequence.

' :Generators of lltriangular pulsesl A,have been known which, however; serve only to prov-ide Vapproximationsloftruly ltriangular pulses. Furthermore, thel'eiigthlo'fthe pulse is diucult to mainwhenlthe spacing'betvveenpulses is large in relationto this length. It is; therefore, aY further Object of iriy .invention to provide a generator of trianglarpulses; which pulses are sepa;- rlted by spees mliii longer than .the nii-lees, in cluding a 'delay line; Nmeans external Vto vvthedelay, line for adjusting thetotal delay through the system, means forvgenerating a pulse ofa definite length startii'lg at" the adjusted 4'delay time, and means responsiveto Athe delayed oulse .for `vgenera 'nga signal'suitable forapplioationtothe delay n e.. "Otherohjects of .this invention are to provide improved details in such a systern,`and` wi1l be reerred to hereinafter. Y The manner in which theseobjects are achieved will be evident from the appendeddescrip'tion taken conjunctionwith thedrawings in which:

Figure 1 is ablock diagrarnof theifentiregen.-

erator;

igure 2 1s a simplified Wiringdagram of a typical vcircuit"embodyin'girly invention;

` Figure -3 is a "detailed circuit diagrarnshowing the constructional constantsof thehsftarting pulse guene'ratorg lFigure 4 shows the details of integrator 4;

-Fi'gurer showslt-he details of delay line driver;

.Figure shows the details ofchfarging circuit 8;

Figure-9 shows the details'Vof'puljse for'rner 9;

Figure 10 showsfthe details ofintegrator IU;

lFigure 11 show`s .the detailsr of pulse width controlcircuit Il;

' rieure IZShQWs the details of discharge circuit Eisiire 13 shows the details of phase, inrerter.

'Eisure 1,4 shows ythe details of starting puiser control circuitvldi' Eigure 15 shows the c letailsy of delay line l5; amp.

'Figure i@ shows the shapes and relative, timing of' the Waves Qcurrinfsj ifi various Darts ofthe YVfhl@ the intention-might be deseribed in geni eraiterms'; Ii believe it iiiorev informative 'to rie- Scribe it SD'Cq@ teiihlsyandhve 1011? giving l iirffiiit constants' for a 'prac'ztical Working (impediment: eiativeiy'aetaueiicirciiiti are. rangement iuustr Figure 2 'of' the' drawing Winv first 'be dieser d" rather generar terms in connectie ithits corresponding block diagram; 'Figure 1. "Attention 'is here directed to the fact ,that the pui'sawayeforms; which' are illus-1 taedzi Fis fe 'fasen-'aid iii undertanding th 0. he system; are, 'in l'ig'iirejifi,V drawn as tfac ontime axis.

In I starting pulse generator 3 is any suitable self-*excitedl scillator'fabable ,of ge Y. aiIieSiJBCd l's t'anr'sitabl rate such f o'reia fp le, f e rate of 40,0`yclesper second'. Generator' 3 serves asthe' statilng'elenieii, h'e system v.and is noi-used in no rn'ial operation. .The siate and the d iifaiioii f th'iiulssgerier:

' are not critical; and any 9i hCuit providingsuch pulses mayb at'. the'ifalte of 4 0 0 pulses per second. w' Integrator 4 @perates ,on the t. it by'istartng pulses, supplied Se" generator 3; to igen een rally triangular pu1ses', their rseltirri.

siicndinetblhe'd atiQIIOf the'aiinleipl ine f aii iiiiiizbei gtadiii ed iii .eine tion. Dur'ir'igthe ta 'ingpoiftion ofthe'c 'le (i operati@ Qi tir 9591, aber' system', wiii and is not 2J partei the active Qi duty-p0 ofthe ycl, the fidelity 0f theiraneula s '0' the pulse generated vby integrator i no Dorian@ '25nd elthlfigh integra@ 4 wiiirciitarrngementsgreeneri er trianguiarV pulses' ofl the type "referred t'p y the 'detailsi'f thel circuit connectionsvvhich roviie'thigfiincoii needinoi' be dsgiibee u conctiospf thefentii circuits are in detail; Howev'ei,'ii 'may'be 'notariat l that there are provided 'feedback'cirfcuits' zfa'nd Sbgbtweerii deiayliiiidiiifry.; ao, ru. which areimprrtaiite eiiieniis`V iiiih i; ise staeingisysten( apiece? Delay line driver is supplied with a suitable triangular pulse by integrator il. The details of this circuit 5 may be disregarded for the moment. In general, driver 5 may include a cathode loaded ampliiier tube, with a cathode load resistor, driving the delay line.

Delay line I5 may consist of a suitable uniform line, or a line of lumped sections, as desired. Suitable circuit constants are given with respect to the detailed circuits shown later, but for the present it is only necessary to consider that the delay line I5 consists of a number of similar sections, each section providing about 4.16 microseconds (In. s.) delay. The delay line may suitably have a 2,500 ohm characteristic impedance, J

and it acts as a low pass filter, preferably with a cutol frequency of 200 kilocycles (k. c.)

The time delay per section is herein referred to as 4.16 m. s., but it is actually i1/6 In. s. per section, which provides 125 m. s. delay for 30 sections. However, if 4.17 1n. s., the nearest approximation were recited, and the user were to adjust each section to this delay, more than the available time would be required, which fact justiies the specication of 4.16 m. s., the smaller, but workable amount of delay.

The delay line I5 is provided with output connections between sections, so that a wave applied tothe input of line l5 passes the output connections successively at times spaced 4.16 m. s. apart. The use made of these output connections will be referred to below, but it is only now necessary to appreciate that after the triangular wave described above has traversed the rst two delay sections it has assumed substantially its ultimate shape, and that the wave shape c-f the signals available at the successive output terminals is sufciently constant for the purpose. Output terminal Ilia of the delay line provides an output signal to variable delay circuit 6. The terminal I5a is connected to a point which is 291/2 delay sections from the input terminal, thus providing a total delay of almost 123 n1. s. The delay line I5 is continued beyond the output point I5a, not only to provide a suitable termination to avoid signal reiiections, but also to provide output connections suitable for use in the multiplex system in which this generator is adapted to be used.

Variable delay circuit 6 receves a triangular positive pulse from the delay line I5 and produces a negative output pulse having a steep leading edge. The time relation between the leading edge of theoutput pulse and the peak of the applied triangular pulse is adjustable, and i delay control element Ea has been represented as operatng on variable delay circuit 6 to provide this time adjustment. The delay time provided by delay circuit 6 is of the order of 2 m. s. The output pulse from delay circuit 6 is applied to diii'erentiator 'I and to integrator l0.

' Because it is necessary to provide pulses of xedy repetition rate and having a definitely timed duration, the signal from delay circuit 6 is supplied to two separate channels to produce the leading and trailing edges of the required output pulse in precisely timed relation. The diierentiator 1 operates upon the pulse applied to it, to provide a sharp positive pulse, corresponding in time to the leading edge of the pulse produced by the variable delay circuit 6. An additional sharp negative pulse is generated by diierentiator 1, corresponding to the trailing edge of the applied pulse, but because the duration of the output pulse from delay .circuit 6 is not controlled, this negative pulse is of no sig-'- nicance and is discarded. The output signal from diferentiator I is applied to charging circuit 8.

Charging circuit Il is adapted to make an abrupt change in the output potential of pulse former 9. Charging circuit 8 may be considered to be essentially a circuit for applying a potential to an energy storage device, such as a condenser, in pulse former 9 whenever a positive pulse is applied to the input of charging circuit 8. It will thus be seen that the output potential of pulse former 9 will change suddenly from one Vahle to another at a time corresponding to the rising pulse from diierentiator 1 which, in turn, corresponds in time to the leading edge of the delayed pulse emitted by variable delay circuti 6.

The sgnal channel including integrator Ill is provided to terminate the pulse initiated by pulse former 9, and thus to control its width. Integrator I0 produces an output pulse which, being the integral of a rectangular pulse derived from variable delay circuit 6, rises at an approximately uniform rate from a nominal zero level. The output pulse from integrator I0 is applied to pulse width control circuit Il.

Pulse width control circuit II is provided with adjustable control element I la which establishes the time at which the output pulse from width control circuit II commences, in relation to the time at which the applied pulse commences. As will be seen hereinafter, only the leading edge of the output pulse is utilized and the trailing edge is discarded. Accordingly, although control element Ila is used to adjust the Width of the triangular pulse to be generated by pulse former 9, no consideration need be given to the eiect, on the width of the rectangular pulse generated by circuit I I, of the operation of width control IIa. The circuit details of pulse Width control circuit II and width control lla might suitably be similar to those in variable delay circuit 6 and its control circuit 6a but, as will be evident later, a modified circuit arrangement is preferable. The output pulse from circuit II is applied Ato discharge circuit I2 to cause the dscharge circuit to terminate the pulse generated by pulse former 9.

Discharge circuit I2 may be considered to be a circuit which places in the energy storage element of pulse former 9 va charge equal in value fand opposite in polarity -to the charge previously applied to the pulse former by charging circuit 8. The pulse former 9 is thus restored to its initial condition.

Pulse form-er 9 thus generates a .rectangular pulse which is precisely timed in relation to the signal from delay circuit 6 and is of adjusted precise duration. The timing of its leading edge is established by the leading -edge of the pulse from delay cricuit 6 through differentiator 'I and charging circuit 8, While the trailing edge of the output pulse from pulse former 9 occurs at a time delayed by pulse width control circuit Il after the leading edge from delay circuit 6.

In the operation of the circuit the variable delay circuit 6 should be so adjusted that the total delay around the entire circuit will be exactly rn. s., corresponding to an 8,000 cycle repetition rate. The portion of the delay line I5 thus used will provide somewhat less than 123 1n. s. delay and the delay circuit 6 approximately 2 in. s., the other elements of the feedback circuit supplying the remainder of the required delay of 125 m. s. Because it is desired to generate a triangular Wave having a i m. s. rise time. andi cludela. tube connected Ias a cathodefollower andr having. two output connections, one.connected to its cathode :and the other to its. anode. Reer.

tangular pulsessimil-ar. in magnitude. but of.y `ope lpositepolarity areprovided by thesetwooutput.

terminals. The output pulse, supplied by. the.

cathode connection of phase inverter I3aisrapplied to integrator. 4.. Integrator 4, functioning.` asa.

triangular. pulsey generator, andresponsive to the:y rectangular. pulsesupplied by. the. device Iii, suppliesa lcorresponding triangular pulse. to delay line. driver 53. for application todelay linehlu.v

Recapitulating., it'` Will. be seen, that, initially,y a. generally;r rectangular pulse, one of thosesupplied. at the ratev of; 40.0. per second by, starting pulse; generator 3;, produces. a. suitable-,triangular pulse from integrator 4 for application through delay. line driver 5' todelay line I5, After a, de; lay.A of about 123,. rn. s., this pulse iS. appliedto variable delay circuit 6.- whose delay time of aomoxlrnately 2v m. s. iscontrolled by controleleinent 6a.` The. lead-ing.. edge. ofiY the outputnulse ispanplied.: through. differentiator 'I- and charge; circuit 8to .initiate a;,1;r ulseL in pulse former -9J Thesame leading. edge., delayed by the operationof inte-` gratorf ld and Widthoontrol circuit i-I vfor atime oontrolledby adjustable width control element lla., operates discharge. Circuit- I2. to terminate the pulse.. .The pulse from pulsefformer Sis then..

applied. to integratory 4 substantially 12,5.. In. s; @itertheepplioationthereto oftheorisinalxstartf inenulse from-thedeyioe 3;.. l

It Willlthusbeeyident that I` haveA` providedq a circuit for generating a series of evenly spaced pulses .erV substantiallytriangular Shape-.Separated by.. Spaces longer than said pulses, saldi circuit comprising; Ineens 4f. for eeneratinganulseei oheneirlgemplitude:durirlethe application there-- to. of; aeentrolpulsese delay. line Iihavinsga deler time leneerthen. the length: of; eaehoi .said p-ulses, Vsaid V delay line lbeing connected izo-,receive @Signal .from .Seid .pulse generator means. 4:, an emrltudeeensitive.Circuits ede-ptedto transmit onlyv these-perte Ofeisnalsenrlied toitwhieli are errenezside f a predetermined amplitudelevel, Seidemrlitude Sensitive circuit beinaonnected to receivea. delayed signal from said delay line I; anl energy storage device 9; aucircuit- 1,1 8, connected to receive a signal fromV said amplitude sensitive circuit 6, and adapted tol change, the amount vof-energy stored in said storage device 9.3 by-` er predetermined amount in one` direction upon-Q receiving a signal from said amplitude sen--V sitiyej, circuit 6; a circuit I0 for generating a p ii secr-changing amplitudeupon thejapplication thereto `oi a control signal, said circuit being connected toreceivea signal from saidam-plitilde-sensitive circuit 6; asecond amplitude sensitive circuit: II connected to receive ka signalfrom said., changing amplitude pulse generator Ill, and adapted tochangethe energy stored in said storagefdevice 9 by l the saidl predetermined amount, and inthe direction opposite to the above-mentioned-direction, upon the signal from said changingarnplitude pulsegenerator Il] reaching` a predetermined amplitude; and means-forlapplying aicontrolpulse derived from said ener-gy storage device-9: to said pulsefgenerator n means 4".

There are.V certain conditions or adjustmento theabove-described generator under which, if thel` oscillations were. stopped by. some. external, cause, the generator might fail to., restart. 'Ilo-adapt this generator for unattended use, itisdesirable.. tov provide some means of; restarting itautomati cally, Whether it was'V stopped by exte1.r1al'means or byfdeenergiza-tionof the power supply. I1oW-` ever, it:` is essential that the. starting mechanism' shall not interfere with thenormal. operationof. thev generator;` A starting system. has therefore; been provided, which starting system; will be: maintained inoperative during the. whole.; time' that the generator is .functioning normally;`

'llhelinitiall pulswas. provided. byV starting. pulse. generator 3=,` and ern-.additional pulse mightbe Bx: pected. tobevgenerated 2;500.m. s.. later.; How;- ever, 'before the next: pulse fis-generated by genera;- tor 3.', the. system has. commenced to generate pulses at. the rate of. 8,009', per secondi.. spaced m. s..apart'. It, is necessary todeenergizetthe devi-oe3 :to prevent; it from introducing a secondl pulse, which would not be synchronized:withtthe; 8,000.. cycle pulsesdesired to be generated; It-,isfor this reasonthatphase. inver-ter I3;Y is provided Withtwo.- output connections..

The outputconneotion from. the anode ter.- minali of'. phase. inverter I3 provides. a. sig-hall tot puiser control circuit Ill.;V Inresponse. toapplied signals.. of( the.. magnitude of, thoser supplied: phase. inverter I3When energized b.y;.8,0.0.0.cycle pulses, control cir-cuit It, generatesya negative; potential'. which. is. applied to a. control element of starting. pulse generatorS. Thisnegativelportential: indicates thepresence of 8,000 cyclepulses inthe pulsegenerating. system andgrenders:start-f` ing pulse generator 3i: inoperative. Vl/henevenV for. any. reason,v Whiletthe system isenergized; there. are... no 8.',000 cyclepulses being. generated; starting; pulse.` generator 3 is:` permitted: tongen erate.- 490 cycle; startingpulses tol resta-rty the. system; Because theunitsSf-andr I-'l/.of Figure:A I-` are used4 only during. the* startof:- the normalL operation. the connections. between theseA units. and the others are shownin.dashedlinesi Fig-ure.: 2 represents'y aA simplified-l connection diagram off a. typical circuit providingtheiuncftions described iwith reference to` Figure l. and includingA some refinements. To lfacilitate.; refs# erence. to thefigures` showing the.- details` andI the .circuitconstants theelements'of each por-A tion of the circuit have been. numbered-Withfa series of reference characters,A eachiof which starts with the number of the 'gure-Whichfshows the.; details. and thecircuit' constants. Furthermore, the circuit diagram is laid outfin thesame patternas is Figure.. 1, to simplify lreference-to the. block/diagram.

Referring in detail to. Figure 2, the puiser-3 includesagaseous thermionic triode 3B, a storage condenser 3| and a charginglresistory 32.. Whenthe grid of triode 30. is` notbiased strongly negatively, the. tube Will cond-uct` wheneverra substantial plater voltage is appliedto it. Assuming. that condenser 3.1. is` initially lsubstan-f tially discharged and 'thatthe tubel 381 is .nonconducting,v condenser SI1 will charge, through resistor 32.1until..its.potential reaches vthe breakdown voltage of gastube. 30. Gas tubettllwill then start toconduct, the.4 current passing from its.: anode toits cathode. and then. toA ground' throughresistor 4I. This .conduction will continue until. thepotentialacross condenser 3| Ais loweredito the extinction, voltage of'. triode v3l).

. Tube-30 iwill thenceaseato. conduct; Thevoltage across condenser 3I will then commence to rise, and the cycle will be repeated. If a negative potential is applied to the grid of triode 30, that tube will remain non-conducting and the pulser 3 Will be inactive. In normal operation the pulser 3 provides pulses which initiate opera- .tion of the pulse generator system. Pulser 3 then is rendered inactive and remains inactive until required to restart the system. The circuit constants of pulser 3 are shown in Figure 3, and are so selected as to produce pulses, having sharp edges, at the rate of approximately 400 pulses per second.

Integrator 4 converts the pulses applied to it into triangular pulses for application to delay line driver 5. During the starting operation the cathode of pentode 4E) receives a positive pulse from pulser 3, although during normal operation no pulses are applied to its cathode, but rectangular negative pulses of 4 m. s. duration are applied to its control grid. The anode circuit of pentode 40 is so connected as to discharge condenser 42 when the pentode is conducting. Condenser 42 is supplied with unidirectional energy through resistors 43 and 44. Between pulses, pentode 43 is conductive to unidirectional current, which passes through resistor 44, resistor 43, pentode 40 and resistor 4I. This resistance chain acts as a voltage divider to apply a predetermined potential across condenser 42. The grid of pentode 4B is held at ground potential by the positive voltage source acting through resistor 45 and across rectifier 45. When a positive pulse is applied to the cathode of tube 40, or the corresponding negative pulse Y to its control grid, tube 40 is rendered non-conductive. The potential across condenser 42 then rises through the time circuit consisting of resistors 43 and 44. When pentode 40 again becomes conductive, at the end of the pulse, the

potential across condenser 42 returns to the value Which it has between pulses. The rectier 4, and the other rectiers shown in the wiring diagrams may be vacuum tube diodes, but are preferably fixed crystal rectiers.

Delay line driver 5 is supplied with the potential across condenser 42. This potential is applied through blocking condenser 5I to the control grid of tetrode 5i). Tetrode 55, acting as a cathode follower, provides an output voltage across its cathode resistor 52. The value of the potential applied between the screen and the cathode of tetrode 55 is maintained relatively constant by bypass condenser 53 connected between the cathode and the screen circuit, and the screen is energized through filter resistor 54. Resistor 53a is used to modify the operating curve of tetrode 5E! for the purposes explained below. The plate circuit of tetrode 50 is supplied with unidirectional energy through adjustable resistor 55.

It will be evident from the description set forth above that the apparatus will tend to produce an exponential rising wave followed by an eX- ponential falling wave, the rates of rise and fall being different, due to the fact that the pentode 40 is cut off during the rising portion but is conductive during the falling portion. Such a wave, while applicable for the purposes of a delay line pulse generator generally, is not suitable for the high precision requirements of certain multiplex telephone signal systems. It is necessary to provide means for adjusting the rates of rise and fall of the triangle to substantial equality and to linearize both the rising and falling portion of the wave. The feedback connections described below, in cooperation with the electrode supply impedances supply these requirements.

As stated above, the purpose of integrator 4 and delay line driver 5 is to produce a generally triangular pulse, having a rise time equal to the duration of the pulse applied to integrator 4, and a similar decay time. The normal charge and discharge curves of condenser 42 through the resistive networks are exponential rather than linear. Furthermore, due to the change in the resistive network due to the change of pentode 40 from conductive to non-conductive condition, the rise and decay times are different. Feedback connections 5a and 5b are included between driver 5 and integrator 4 to linearize the rise and fall of the potential across condenser 42 and to equalize the rise and decay times of the pulse. In addition, resistor 53a is included in the screen circuit 0f tetrode 53 and resistor 55, included in its plate supply circuit, is made adjustable, while the Value of the potential applied through resistor 49 to the screen of pentode 45 is also made adjustable. When using the values set forth in the detailed iigures, Figures 4 and 5, or any other corresponding set of Values, it will be found that the adjustable elements referred to above may be so adjusted that the output voltage applied across resistor 52 will be sufficiently nearly a triangular wave for the` purposes of this circuit. Feedback connection 5a applies a negative pulse from the plate of tetrode 5t to the screen of pentode 40 through blocking condenser 4l while feedback circuit 5b applies a positive triangular pulse through blocking condenser 56 to the junction between resistors 43 and 44 so as to modify the wave shape of the potentials applied to condenser 42 during the generation of the triangular pulse. The resulting triangular pulse generated across resistor 52 is applied to the 2,500-ohm delay line I5.

As stated above, the generally triangular wave is applied to delay line I5. Before the wave reaches tap #l the rst effective output terminal of delay line I5, it assumes a predetermined wave shape which diiers slightly from the shape of the wave across resistor 52. This new wave shape is maintained while the wave traverses delay line I5, and when the wave reaches tap #28'1/2, twentynine and a half sections from the input terminal of the delay line, it still has the same shape which it had when passing the earlier output terminals, but a somewhat smaller amplitude. This generally triangular pulse from output terminal I 5a is applied across potential divider 5I-52 to variable delay circuit S.

Delay circuit 6 is insensitive to the portions of the applied signal below a predetermined level but produces a substantial response to all applied signals above that level. It is prevented from responding to signals below the predetermined level by the negative bias on the grid of pentode 60 provided by rectifier 63, the anode of which is biased negatively to anadjustable amount by potential divider 64. Unless rectifier 63 is a crystal rectifier it should be provided with a high resistance leakage path. Blocking condenser 65 permits the rectifier 63 to thus establish the normal operating conditions of the circuit. When the applied positive triangular pulse arrives at the grid of pentode E0 no plate current flows therein until the time when the voltage ofthe pulse has risen to the cutoff value of the pentode, which is less than the negative voltage of the anode of rectifier B3 as established by potential divider 64. The subsequent rising portion of the positive pulse is effective in producing an amplified signal at the plate of pentode 60. The pulse reaches its maximum Value and its potential commences to fall. It falls to a value corresponding to the cuto potential of pentode 60, when no further current flows in the plate circuit. This output pulse is of the order of 2 m. s. long. It will be evident that the time at which pentode 60 commences to transmit the pulse will depend on the potential across divider 64 in relation to the time and voltage characteristics of the triangular pulse across resistor 6|. The negative pulse produced by pentode 60 is available across resistors 66 and 61 in its plate circuit, acting as a potential divider. The entire negative pulse is applied to integrator l while the same pulse, attenuated, is applied to differentiator 1. It is to be noted that the pulses applied to integrator l0 and differentiator 1 comf mence at a time which is delayed with respect to the beginning of the pulse available at terminal |5a, which time may be adjusted by adjustment of potential divider 64, and is usually set at about 2 m. s. The arrangements in this circuit which overcome the diiculties introduced by the ow of grid current in tube 60 are described in detail with reference to Figure 6.

Differentiator 1 includes pentode 10, the grid bias of which is established by rectier 1| and grid leak 12, the grid leak being connected to a positive potential. The input signal from delay circuit 6 is applied through blocking condenser 13 as a negative pulse, which results in a positive pulse across plate load resistor 14. positive pulse from resistor 14 is applied through condenser 15 to grid leak 16, which is connected to a negative potential. The time constant of the condenser-resistor combination 15-16 is so small that the leading edge of the positive pulse applied thereto produces a, sharply rising and falling positive pulse, While the trailing edge of the applied pulse produces a sharply falling and rising negative pulse some time thereafter. These sharp pulses are applied to charging circuit 8.

In order to provide regularity of operation of the circuit 9 which forms the pulses, it is desirable to charge it to exactly the same potential during the generation of each pulse. It is then necessary to discharge it to substantially the si same potential after each pulse has been generated. The potential to which it is discharged need not be maintained as exactly as the potential to which it is charged. To provide this result it was necessary to devise a circuit operating to establish a definitel potential across the condenser 60 when it is forming a, pulse, and to connect the condenser S0 to a second definite potential to discharge it. The charging circuit 8 is utilized to provide the deiinite level of charge.

Charging circuit 8 includes pentode 80, which is so biased as to be unresponsive to applied negative pulses. Pentode 80 responds to the rising pulse. It does -so by becoming conductive for the duration of the positive pulse, a very short .E

period of time. During this time it establishes the potential across pulse-forming circuit 9, specically across condenser 90, at a denite low value corresponding to the potential of the anode of pentode 80 when no current is flowing.

vIntegrator I0 is used in the part of the system which determines the length of the ultimate output pulse. This arrangement is necessary because the trailing edge of the original triangular pulse was discarded by the operation of pentode 10 of delay circuit 6. The new trailing edge vis established in relation to the new leading edge by generating a pulse at a denite time after the leading edge of the pulse from delay circuit 6, and using the pulse thus generated to terminate the outgoing pulse.

It is possible to so adjust delay circuit 6 that the duration of its output pulse is less than-l m. s. Under these conditions the output pulse cannot be applied to integrator I0 so as to produce an output pulse therefrom 4 m. s. after the beginning of the pulse from delay circuit 6. It was, therefore, necessary t0 devise a pulse lengthening circuit which will continue to energize integrator |0 for at least 4 In. s., regardless of the duration of the applied pulse. Integrator l0 includes a pulse lengthener which consists essentially of condenser |0|, which is charged through resistor |02 from a positive source. In the absence of an applied pulse, the positive source is grounded through resistor |02 and rectifiers |03 and |04. Blocking condenser |05 permits this condition. Upon the arrival of a negative pulse, rectifier |04 is rendered non-conductive and rectifier |03 connects the negative pulse to condenser |0| to charge it negatively. Immediately upon the termination of the appliedv negative pulse, condenser |0| starts to draw current through resistor |02, and its potential continues to increase in the positive direction until the upper terminal of condenser |0| reaches ground potential, at which time the rectiers |03 and |04 become conductive to hold the voltage across'condenser |0| at zero. In this manner the potential applied to the grid of pentode |00 will go negative at the beginningy of the applied pulse and will commence to rise after the termination of the applied pulse, about 2 m. s. later. The grid potential will continue to rise linearly, for about 4 m. s., and until it reaches zero potential.

The plate current of pentode |00 is cut oi for approximately 4 in. s., this providing a widening of the 2 m. s. pulse supplied by delay circuit 6. During the 4 rn. s. that theplate current is cut off, condenser |01 charges through resistor |06 in such a direction that the terminal of condenser |01 connected to resistor |06 is becoming more positive, thus providing a rising integrated pulse. The resulting integrated pulse is applied through blocking condenser to pulse-width control circuit `A feedback connection is provided through blocking condenser |01 for the purposes to be described below.

The delayed integrated pulse is applied through blocking condenser to the grid of tube |0. Rectier ||2 is rendered normally non-conductive by the application of a negative potential to its anode by voltage divider ||3 and continues to l remain non-conductive until its cathode voltage exceeds the negative potential of its anode. The principal function of rectifier I2 is to prevent a change of reference potential of the grid circuit due to a negative charge of more than the tap potential of potential divider I3 remaining on the grid side of-grid condenser caused, for example, by the flow of grid current in tube |00. Rectier ||2 should either be a crystal or other rectifier with internal leakage, or should have an external leakage path. The operation of this arrangement is described with reference to Figure 6. The integrated pulse ordinarily produces no change in potential across rectifier I2, which isA used to establish the large negative bias on triode l0 which prevents triode I l0 from responding to the early part of the in- -inences` to'Y flow in triade I IU'.'

Ylil teg-rated pulse from integrator.: I i Thetimef. at which-.theplate-current` of triode I I :commences Y is.i determined Aby the time' when :the :integrated pulsenreachesna value established by the-vsetting offpotential divider. II3.V Potentiakdivider II3 may be adjusted overravwide rangezorjvaluesto thusradjust thev timeiatwhich plate'fcurrent com- The `pulse in: the platecircuit of vtriode-I I 0 :bears a'rxedtirnerelai tion to the'pulse-appliedv to integrator I0,' which is occurring; simultaneously Vwith :the pulse I applied to d-iii'e'rentiator'1.v In this'mamier the 'time when the :output .pulse fromv triode `I I commencesmay bef' adjusted: in: 1 relation 1 to: the time. when i the correspondingpulse hisfapplied' vtoi diii'erentiator 'I In .rn'actice; thenadjustmentV is such that ther outputaofftriodeivl Iis' vdelayed for 41m.V s. after vthe pulses.applied:to` differentiator. 1I" Triode I I 0 is provided. with loadfresistor III; which'- isf: connested to:a:sourceof positive potential.` The-out 4value.` RIesistorl II'isv connected'to a positive source' to apply anode vpotential'to triode I I1 and toA act as la. load resistor: Thevr positivey pulse generated'across'load resistor I I 8-is applied through blockingcondenser |01 to-V load resistor- |06" of pen-todefll). The/'pulse fromthe-anode circuit of "tr-iodev I` I'I fisfsopolarized as-'to add to the 'voltage generated' across'resistor 106'. However, it is' to bediotedthat the output pulse from'triode I I'I, being 'derived 'from' the upper portion ofthe pulse across-re`sistor |06, will only commence to add voltageY acrossv resistor- IDB four microseconds aftertheepulse across resistor IDS-begins to rise, The result of the regenerative `feedback'through triodeI I1 is to cause'a-steeprisefof the pulse ap plied` to the grid oftriode. I Iatexactlythe time thatfA triodeA III). becomes conductive, thus enhancing 'the eie'ct of I' this tube.

triode I l'willtherefore. have a sharply falling forward edge, even though it was ,derived from a. sloping wave,. generatedjby the integratorcircuit I Dill D21 The resulting negative. pulse across :resistor I I 6' is applied fto. dischargacircuit I 2 Inl spiteoflthecare.whichhas Vbeen applied to thesystemlfor establishing the levels, between which the pulse. across condenserv 90 isformed,

other refinements are possible, particularlyin the mattertof applying a predetermined and tdei-irrite voltage` .to the discharge tube I2 I 'l whilethe discharge :of condenser 90'istakingplace.' Ihave provided. such `a furtherrenement which is incorporated in discharge. circuit I 2i The :pulse-fromipulser Width control .circuit II, applied to'discharge circuitzI2, is' :theremodiied soras to provide for the discharge of condenser 9D exactly four *microseconds* after its potential was established by; pentode 8B. Discharge circuit' l2 includes triode I \and"triode I 2|. The grid potentialof triode is maintainedat'zero by the operation of 'rectifier |22 except during the application oi a:r negative pulse throughblocking con- The negative `pulsethus'produced'across. load resistor IISof I2 denser' |23.I Grid leak' I2'4 isreturned toi a: positive source for; this purpose, whilethe cathode `of triode-x |25 isi connected" toa positive-:potential source of low value; Triode-I'Z acts.L to produce apositivepulse across load resistor |25 AWh-ichis connected to. a positivev potential source;Y The maximumv positive potential Yacross resistor- I25 is limited by'rectiiier I26'whoseA cathode is connected toa positive biasing source. The resulting :positive pulse lhaving -a sharply rising leading edge and a lflattop is-a-pplied tothe gridof charge triode x I2 I Triode YI 2 I receives -its plate current through plate resistor I281Wh-ich is .connectedfto a positive potential-source; This positivesou-rce provides :the platecurrenttor pentode 88, as well Yasftriodel I2I; but `thev plate. current-v energy is stored 'in pulse-forming condenser-90'. There-is no timewhen both triode.V I2I and -pentode 80- are conductive. In summary, it will :bef seen that the negative potential applied lacross -condenser 38 'by the operation -of pentode will be removed 4,substantially instantaneously and toa vdeiniteievel, at a time Vfour-microseconds afterit Was placed thereon,.by;the operationof triode yI 2 I in response Vto-the sharpleading edge and the atvtopot-'the delayed 'pulse generatedl in delaycircuit I I. The negative pulseffrom pulse 0iorrner 9 is applied. to phase inverter circuit' I3;

It iszto bey noted thatfthe time: .duration'cf fthe pulse acrosscondenser is unaffected byladjustmentor potential dividerV 6# which adjusts the repetition rate 'of 'the'puls'es Similarly.;l it will be evident that the repetition. rate' of. the." pulses across condenserB will' be entirely' unaiected 'by the adjustment-of their duration by manipulation of potential divider II3.

Phaseinverter I3 includes -triode 30; provided with cathodeV loadv I3I-I32` and platerload |33 so asto generate two simultaneous pulseslof opposite'v phase. Negative'pulses applied through blocking condenser I3!!l are applied across-- grid leak |35- a-nd output'resistorA |32. Gridbiasis established lby the flow` of plate current through resistor I3I. Plate current is provided bythe positive source, through load'resistor`l33; The negative output pulse'fronr the cathode is applied to the grid ofpentode Il!)i ofintegratordiwhile the positive output pulse across resistorA I 331s appliedto puiser control'circuit I4. The negative-pulse for application to the gridof integrator 4 is appliedacross grid leak' through blocking condenser 48, that grid being normally. maintained at ground potentialv by rectiiier Mi;y Ref'- erence to.. the description., of. the operation. of integrator t-will show that the negative :pulse applied to .thegridcircuit of pentodeflisexactly-the` pulse required to vprovide the desiredtriangular pulse for application'to delayy linef I5. Bearing inmind'thatthct delay time in the delay lin-e I5: between the time of'applicationof the pulse to the-input terminalvand'itsY arrival at the:l output" terminal: I5a is approximatelyl 123 in. s; and'that the delay in-delay circuit 6 is so adjusted that theA total delay between: the arrival of the pulse .at'iterminal Iaand the commencement of the new4 pulse. generated" across resistor521of delay lineidriver 5 is approximately 2 In.y s., it will berecogniz'ed that potential divider ed providesan adjustable element for setting the time. between'. the:v commencement of the pulses atzexactly 1n. s x This corresponds to arepetitionfrate' ofSgOOdper second, which is a value suitablerfor pulse transmission of signals Aup to 33900. cycles per second, the upper frequency limit at which the circuit, to which this generator has been applied, is adapted to operate.

In providing means for rendering the starting circuit inactive during the normal operation of the generator, it is preferable to have some simple and reliable means which ascertains that the generator is operating at the normal frequency and renders the starting circuit inactive.

The connection between cathode follower I3 and pulser control circuit |4 has been drawn as a dashed line to emphasize the fact that it is not part of the normal pulse generating system, but is simply auxiliary. The positive pulse across resistor |33 is applied through blocking condenser |4| to the grid of triode |40 across grid leak |42. To simplify the direct current potential relations/in the plate circuit of triode |40, the plate circuit is returned to ground through resistor |43 and time circuit |44, while the grid and cathode are returned to negative potentials. The cathode is grounded through bypass condenser 145, and bias resistor |45 is provided with current through resistor |41 as well as through tube |40. The bias arrangement is such that triode |40 is normally non-conductive. Tube |40 conducts when a positive pulse is applied tc its grid circuit, thus producing a pulse, which is negative with respect to ground, across resistor |43. This negative pulse is applied through resistor |48 to the grid of pulser tube 30. Condensers |49 store this negative potential, which discharges slowly through resistors |43 and |44. The discharge time is made longer than 125 m. s., which means that during normal operation of the generator a sufficient negative potential will be maintained on the grid of triode 30 to prevent the generation of pulses by pulser 3. The discharge time of condensers |49 is so adjusted, however, that it is shorter than 2,500 m. s., which is the time between the pulses normally generated by pulser 3 in the absence of negative voltage on the grid of triode 30. This arrangement permits pulser 3 to generate pulses at a'400-cycle rate until the main oscillating system goes into operation, establishing and maintaining a suicient negative bias to stop the operation of pulser 3.

The approximate values of the potentials at thesupply points are set forth in the wiring diagram of Figure 2. The detailed figures, 3 to l5 inclusive, give all the necessary values, includingthe tube types and the values of the decoupling networks, for a practical working embodiment. All of the voltages indicated on the detailed figures may suitably be obtained from a regulated power supply having output terminals supplying +300 volts, +150 volts, and -150 volts, the remaining terminal being grounded. The values of the components have been indicated in many cases as odd values. The reason for this is that, in practice, the color coding which designates the value of each of these components is such that the selected values are more easily recognized than similar components having round number values. It is to be understood, of course, that, unless a value is indicated as critical, it may be considered to be approximate, and a component having a value within lO or even 20 percent of that specified can be expected to be suitable.

In view of the facility with which reference may be had to the descriptions of the construction and functions of the various portions of the circuit, by referring to Figure 2, these descrip- 14 tions will not be repeated during the discussion of Figures 3 to 15.

Figure 3 shows the constructional constants of the starting pulse generator 3. The only element as yet undescribed is choke 33. Choke 33 serves'to prevent undesired radio frequency oscillations in the circuit including gas tube 30, without interfering with the useful functions of this circuit.

Figure 4 shows the details of integrator 4. Potential divider 44a adjusts the supply potential applied through resistors 44 and 43 to charge condenser 42 during the time that pentode 40 is cut on?. The amplitude of the resulting charge on condenser 42 depends on the setting of potential divider 44a. The voltage fed back from delay line driver 5 to the junction between resistors 43 and 44 serves to modify the supply voltage during the time when a triangular pulse is being formed. This feedback assists in linearizing the rise and fall portions of the triangular pulse. The screen of pentode 4Q is supplied with potential through resistor 43. The potential divider 49a sets the normal operating voltage of the screen and thus controls the plate current of pentode 40 during the time that it is conducting. The setting of potential divider 49a thus has an effect on the shape of the fall of the triangular pulse, but it has no effect o-n the shape of the rise, because pentode 40 is cut off during the rise time. In addition, `a negative triangular pulse corresponding in time to the output pulse of driver 5, but of reduced amplitude, is fed back through condenser 41 and across resistor 49, and is applied to the screen of pentode 40, to further modify the falling portion of the triangular pulse.

Referring to Figure 5, the details of the plate decoupling circuit 51 are illustrated. In addition, potential divider 58 is shown as providing the potential for the grid of tetrode 50 through grid leak 59.

Figure 6 shows the details of variable delay circuit 6. The values of plate decoupler circuit 68 and screen potential supply circuit 69 are indicated on the diagram. During normal operation of the circuit, the amplitude of the positive peaks of the applied triangular pulses may be sufficient to overcome the negative bias supplied by potential divider 64, and to cause the fiow of grid current in tube $0. This will cause the grid side -of condenser to charge negatively, and this charge will be added to the bias nominally established -by potential divider 64, and the sum of these voltages will control the amplitude level at which the next pulse will produce plate conduction in pentode E0. |The delay time is controlled by the effective grid bias on tube 60. Therefore, if no provision is made to overcome it, the presence of this negative charge will result inl a change of the time at which output of delay circuit B will commence, in response to the incoming wave. This will result in a change in the delay time in circuit 6. This means that changes in other elements of the circuit than potential divider 04 can modify the delay time, and therefore the repetition rate, which makes vprecise adjustment dimcult. I have, therefore, found it desirable to provide means for establishing a definite level above which the conducting point of tube E@ may be adjusted, so as to avoid interlocking of controls. The apparatus providing this result is incorporated in delay circuit E, and also in pulse width control circuit Il, where'the same problem arises. Rectifier B3 is provided with a negative potential on its anode by potenaereos? tiafr divider 6'4. The normal leakage: of rectifier 63 will initially bias the grid of'pentode iilto the same Vpotenti'al asthatv of. the tap on. voltage divider W1, thus charging. condenser 65.. In the absence of a pulse, therefore, there isno potentialacross-re'ctier 53. After the grid-` of tube 60 has been driven upto zero-biasA by the incoming pulse, and' condenser 65 has thus been charged negatively on the grid side, the amplitude oiT the pul'sewilllfall, the-charge remaining on` condenser 55 The rectifier G3 is sopoled asto prevent the grid side of condenser 55' frombecoming more negative than the voltage of potential divider Se', sowhen thesumof the condenser voltage and the instantaneous voltage of the applied wave reach-the voltage of: the potential divider Sli, rectifier B3 commences tol conduct, and holds the grid of tube. 6@ at this potential. Condenser 65 thus discharges through rectiiier 53, permitting the gridbiasto return to the original datum level. 'Ihis datum level' thus applies to each pulse received from* delay line i5, which renders the circuit conditionsy uniform.

Figure 'T' shows the details of dilerentiator 1. Plate decoupler 11'- -and screen decoupler 1'8 are illustrated' andy the values are specified. Network '9 acts as a coupling' network in supplying the pulse tocharging circuit 8, and alsov serves to supply suitable negative grid operating potentials to pentode 80.

Figure 8i shows the constructional constants of charging circuit 8. The potential divider consisting of resistor 8| and resistor 82' supplies a suitable l'ow screen voltage for pentode 80. CondenserA 83, Vin conjunction with resistors 8| and 82, serves to decouple the screen current from the power supply. It is tobe noted that pentode 8U is normally nonconductive and is only rendered conductive upon reception of a positive pulse from diierentiator circuit 1. Upon becoming conductive, pentode 80 connects the upper terminal of. pulse forming condenser 90 substantially to ground.

Figure 9 shows pulse forming condenser 00 which is.v illustrated separately to emphasize the signicance of its functions.

Figure l showsv the constructional details of integrator |20. Thev screen decoupler circuit'consisting of resistor |08 and condenser |09 is illustratedl Itis to benoted that the load impedance into which pentode Hiii works is apparently the 270,000` ohm plate resistor |05. However, whenever-triode H0 of pulse width control circuit is conducting, triode |J1' of that circuit is feeding back,.by way'ofk capacitor |01, a voltage to resis tor I'DSW-hichadds to the voltage supplied thereto by tube; |00. Consideringv the alternating current conditions in this circuit, the actualv load of tube |i|l01is. load resistor I8 in control circuit samedi-lied in effect by the operation of feedback tube tt'iin that circuit..

Referring to Figure 11, rectifier 2 performs the' same functions as those described above with reference to rectier 63 in Figure 6. The plate potential divider and decoupler |19 is illustrated detail, and the cathode biasing circuit for triade; HT is also shown.

Referring to Figure 12', which shows the details of discharge circuit IZ, itis to be noted that the value of. resistor is critical and should be held within 5. percent. This is because the amount oiv charge removed from pulse forming condenser 90 during the operation of triode |2|, depends on the amount of grid excitation voltage Supplied. to' trode |2| across resistor |25. The

plate decoupling network |29` for tube |2| and the cathode biasing: network for tube |20 are shown in detail'.

Figure 13'shows the details of'phase inverter t3. The` plate supply decoupling circuit consisting of resistor and condenser |31 is shown in detail.

The detailso Figure-14 have all been described above with reference to Figure 2.

The. constructional details'of delay line l5' are shown'v in Figure l5. As stated above, this delay line actsr as. a 200 k.c. low-pass lter having a characteristic impedance-of 2,500 ohms.l It consists of 5|F similar sections having the values set forth inthe iliustraton. As set forth above, each section. provides a delay of four and one-sixth microseconds; Input'terminal |-5 |1' supplies energy to the rst. half of the input section, which half.- section` comprises inductances |52 and shunt condenser I5'3f. The second half-section consistsy of series inductances |54 having the same values as inductances |52, and shunt condenser |55-, which is padded by padding condenser |56. In adjusting the delay line f or normal'. operation, the padding condenser of each section is adjusted, the adjustment beingY made with respect to overall delay rather than delay per section'. This is to prevent accumulating anV error in the delay time. The other'secti'ons of thev delayv line have' similar constants, and the delay line is provided. with a termination consisting of series andshunt inductances |51 of equal value, shunt condenser |53, and load resistor |59; In practice, potential dividers having: an overall resist".- ance of the order of' 100,000 ohms, many times the characteristic impedance of the line; are shunted from each tap point to ground. Signals of suitable amplitude are available across these potential dividers for use in the multiplex signal system with which this generator is adapted to operate. After the applied triangular wave has Y traversed the rst two sections and has arrived at tap #1, it has assumed substantially its ultimate shape, and no significant change occurs in this shape at least until after the wave has passed the middle of section 29. As stated above, the wave is taken off the line at a point designated tap #281/2 and supplied to variable delay circuit 5'. By selecting this particular tapping point on the line, theA changesr which occur in the remainder of section 29 and in section 30, due to the reections from the terminating sections, produce no harmful effect on the wave supplied to the conductor |5a. While the termination illustrated, and consist-- ing of elements |51, I 58 and |59 does not completely avoid reiiections, it is entirely adequate for the purpose. The wave atV tap #30 is subject to about the same amount of irregularity as is the Wave at tap #1. Another section may be includedbetween tap #30 and the termination, if desired. It is unnecessary to provide a termination at the inputv end of the line. Terminal I5| is energized by delay line driver 5 across a 100,000-ohm resistor 52, at appropriate times. The effective impedance of' tetrode 50 is small compared to 100,000 ohms during its conduction period. During the remainder of the cycle, tetrode 5t is out oi and the input end of the delay line i5 is shunted by 100,000-0hm resistor 52.

The values utilized in a suitable delayl line are set forth in Figure 15. It is to be noted that if the values of the elements of the delay sections are not; held within tolerances of plus or minus one percent, di'iiculties in the Way of irregular operation may be encountered. The mutual inductances should also be carefully adjusted.

In order to understand the use to which this system is applicable and the requirements which must be met, brief reference will be made to the remaining portions of the system. These remaining portions will not be fully disclosed herein, as they are described in detail in my copending application, Serial No. 70,951, filed January 14, 1949.

Briefly, a modulator circuit is connected to every tap on delay line I5, except to taps and #281/2. Each of the modulators is also connected to receive an audio signal from a signal channel through a low-pass filter having a cut-off frequency of 3,900 cycles or less. The outputs of the modulators are combined in a single multiplex output circuit. It will thus be seen that, in essence, the pulse traversing the delay line acts as a switching agent to switch the associated modulators on and off at the proper times to apply samples of the incoming signals to the multiplex circuit in a precisely timed sequence.

Figure 16 shows the wave shapes existing in the various parts of the system, with approximate voltage values. Curve A shows the shape of the pulse on the grid of tube 40 of integrator 4 during normal operation. Curve B shows the pulse fed through condenser 5| to the grid of driver tube 50. It is to be noted that curve B is derived from curve A by the operation of the integrator system including condenser 42 in cooperation with feedback through feedback connections 5a and 5b. Curve C shows the triangular pulse fed to the delay line l5.

All of the above pulses are represented on a time scale starting at the time t=0. The remaining curves of Figure 16 are drawn on a time scale starting at t=125 m.s. They represent either the same pulse shown in curve C after it has traversed the delay line, or the immediately preceding pulse which serves to inititate the pulse shownin curve A.

Curve D shows the shape of the pulse in output connection |5a of the delay line. The modification of the shape of this pulse from that of curve C occurs almost entirely in the first portion of the delay line up to tap #0. Curve D, therefore, represents the shape of the pulses available at all of the taps. Curve E shows the wave shape on the grid of delay tube B0, as modied by the operation of condenser 65 and grid conduction in tube 60. The top of the wave has been limited and the falling portion is steeper than that of curve D. The grid cut-off voltage of tube 60 is indicated by a dashed line. Curve F shows the plate voltage of tube 60 and the shape of the wave transmitted to diierentiator 1 and to integrator I0.

Curve G shows the plate voltage of tube 10, as applied to the differentiator circuit consisting of condenser and resistor 16. Curve H shows the voltage across resistor 16, as applied to the grid of charge tube 80. Because the tube 80 is operating with sunicient negative potential on the grid to keep it normally cut off, it only responds to the rising portion of the wave H. The portion below the normal level is shown in dashed lines, to indicate that it is ineffective in operating tube 80.

Curve I shows the voltage applied to the grid |00 of integrator |0, as derived from delay circuit 6 and modified by the pulse stretcher consisting of condenser |0|, resistor |02, rectifiers |03 and |04, and condenser |05. The cut-off grid voltage of tube |00 is indicated as a. dashed line. Curve J shows the plate current of tube |00. Curve K shows the voltage at the junction between the anode of tube |00 and condenser |01. Condenser |01 will start to charge as soon as the plate current of tube |01] commences to fall. As soon as tube |00 reaches cut-off, the rate of charge of condenser |01 will be such that the voltage will rise substantially linearly. In the absence of tube ||1, this linear curve would continue until the tube |00 would begin to draw plate current again, at which time condenser |01 would begin to discharge instead of charging.

Referring, for the moment. to curve L, which shows the voltage on the grid of tube ||0, it will be noted that the voltage rises substantially along a straight line until the cut-off grid bias voltage of tube ||0 is reached. This cut-olf voltage is indicated in curve L by the dashed line. As soon as tube ||0 commences to conduct a signal, it is applied to the grid of tube I|1, the anode circuit of which drives the other terminal of condenser |01 positive. As shown in curve K, this results in an almost instantaneous rise in the voltage at the terminals of condenser |01. This rise continues vertically until the grid of tube ||0 begins to draw grid current, as a result of which tube ||0 is no longer effective as an amplifier. Tube ||1, the grid of which had already been driven considerably negative, is thus held at the same signal level and substantially no further signal is fed back to condenser |01. Only enough signal is fed back to condenser |01 to permit a rise in the plate voltage of tube |00 at a low rate. This rise in voltage will be applied to condenser and will maintain the grid of tube ||0 at the grid current point. This explains the difference between curves K and L. As soon as the plate circuit of tube |00 commences to draw current, it starts to discharge condenser |01 and the voltage on the grid of tube ||0 starts to drop. This results in the beginning of the positive signal across load resistor ||4, which is applied to the grid of tube ||1, to increase its plate current. This increase in plate current produces a negative voltage which is applied to condenser |01. In this way both the plate circuit of tube |00 and the cooperative feedback relations of tubes ||0 and ||1 contribute to the rapid fall of the voltage on the grid of tube I l0, so that it is cut oif almost instantly.

Curve M shows the voltage on the grid of tube |20. It is to be noted that the voltage falls sharply at a time 4 m. s. after the rising pulse shown in( curve H. The length of the pulse. shown in curve M, is of no moment and is determined by the time when plate current commences to flow in tube |00.

Curve N shows .the potentials across condenser 90, as applied to the input of phase inverter I3. The falling portion of the pulse is established by the operation of tube 80, under the influence of the rising pulse shown in curve H. The condenser is then le'it floating and unable to either charge or discharge. c At a time 4 m. s. later, it is discharged by the operation of tube |2| under the influence of the plate current wave of tube |20, corresponding to the grid wave shown in curve M. The pulse shown in curve N is applied, through phase inverter I3, to integrator 4, where it appears in the form shown in curve A.

It will be evident that the apparatus of my invention will provide the same function as a radial beam switching tube when used for switching purposes,;but that the various elements may 1'9 `be much more readily .adiustedaand :maintained .by the operators.

Although my invention has'been described'with Vparticular reference toA a specid. preferredl embodiment, it Will be apparent vthat. the invention is capable of other forms: of` physical expression, and is, accordingly, limited only.v bythe spi-rit and scope of the appended claims.

I claim:

1. In a circuit for generating a seriesfof evenly spaced pulses of substantially triangular shape separated by spaces longer thansaid pu1ses, said circuit comprising: a first. means responsive: to the application theretocf a control pulsevfor generating. a pulse or changingamplitudef; av delay line having a delay time longer than the` length of each of said pulses, said .delay linebeing connected to receive a .signalxfrom said rstypulse generating means; an amplitnde.-sensitive;l circuit adapted to transmit onlyv those parts .of signals applied to it which .are on :one side'of a predetermined amplitude level'. said amplitude-sensitive circuit being connected-to.; receive-.a delayed signal from said delay line; .anenergy V'storage device; aY circuit connected vto receive Y.a signal from said amplitude-sensitive .cir.cuit,.and adaptedito change the amountof lenergy fstoredin: said storage device by a,predetermined.amountrin.one direction upon receiving. a signalfrom said Vam.- plitude-sensitive circuit;v asecondfmeansor. geinerating a pulse of changing amplitudefuponthe yapplication thereto of a control'signaLsaid lastnanied means being connected to .receive a. signal from said ainplit11de-sensitive'.:circuit:v a Second amplitude-sensitive circuitcormected Jto receiveia signal .from vsaid .secondVv pulse generatingmeans, and adapted to changethe=energystoredinsaid storage device by the:said'predetermirredamount, and inthe direction opposite-to.theabove-mentioned direction, upon.. they signal from said changing amplitude lpulse `generator reaching Va predetermined amplitude; .andmeansfor applying a; control signal lderived from. said .energy storage devicev to said` first pulse generating means.

2. Ina circuitfor generating aseries of .evenly spacedpulses of substantially triangular shape separated byspaces longer than-.said pulses, said circuit comprising: aqrst integratorcrcuit. for

generating a linearly rising Wave duringtheapplication thereto of a .rectangular` control pulse; an ampliiier circuit cooperatively associated with said iirst integrator for producinga linear wave falling at the same rate as said rising wave upon the termination ofV said rising wave; a delay-line having a delay time longer "than the" lengthL nof each of said pulses, said `delayline being lconnected to the output of said ampl'ieryai'irst amplitude-sensitive circuit adapted to vtransmit only those parts of signals applied to-itwhich are above an adjustablyf predetermined Iamplitude level, said amplitude-sensitive circuit i being 4connected to receivea delayed triangular; signallfrom said delay line; a circuit adapted -to differentiate signals applied thereto, 'said l circuit Vvbeing.: con nested to receive vsignals-#from said -rst `VAamplitude-sensitive circuit; a. condenser; YaU-circ-uit adapted to charge saidrcondenser` upon receiving a signal, and connectedltok receive/signals-from said diferentiator; a secondintegrating-circuit for producing an integrated pulse-of longer-duration than the pulses-applicdftheretofsaidisecond integrating circuit being 'connected tori-receive pulses from-said rst amplitude-sensitive-circuit; a :secondamplitude-sensitive@ circuit; comiected'ifto receive integrated pulses from said second integrating circuit; a circuit adapted to discharge said condenser upon receiving a signal, and connected to receive signals from said second amplitude-sensitive circuit; a second amplier connected to respond to a signal present across said condenser `by producing a rectangular pulse signal; and means for applying the response signal of said second amplifier to said rst integrator circuit.

3. In a timing generator, a delay line having a selected number of output taps each of which is connected to serve as a source of timing voltage, the total time delay of said line in one direction from the input terminal thereof to the furthest .tap being predetermined, a pulse-forming net- Work,y means for connecting said network to the input terminal of said delay-line, normally7 `inactive initiating means for applying a pulse to the input terminal of said delay line while said pulsef-orming network is de-energized, a time-delay circuit, means for connecting said time-delay circuit to a point on said delay line intermediate said input terminal and said furthest tap, means for .applying the output of. said time-delay circuit to control the formation of a p ulse in said network, and means responsive as a function of the formation of a pulse by said network for Arendering inactive said initiating means.

4. A timing generator in accordance with claim 3, in which the delay time. of said timedelay circuit combined with `the time delay introduced py said pulse-forming network is substantially equal to the ltime delay of that portion of said delay line lying between said furthest tap andthe point on said line to which saiddelay circuit is connected.

5. In a generator of self-sustained, pulses, a delay line having a predetermined delay period between input and output terminals, said pulses appearing at the output terminal of said delay line at regularly-recurring intervals during operation of said generator, a manually-adjustable delay unit connected to the output terminal o f saidv line so as to receive the pulses appearing at such point, a rrectangular wave-forming circuit, means lfor differentiating the kdelayed pulse; output of saidmanually-adjustable delay unit and forapplying such differentiated pulses to said rectangular wave-forming circuit respectively -to control .the formation of the leading edges of the rectangular Waves produced thereby, means `for integrating the delayed pulse. output of said manually-adjustable delay unit and-for applying suchzintegrated pulses-tor said rectangular `waveforming4 circuit vrespectively to control .the-formation of. the trailngxedges of 4the rectangular Waves produced thereby, a generator for .generatingftriangular pulseszin response: to rectangu- Iarr..p;ulses .applied thereto, means for applying the :output of said rectangular wave-forming cir;- cuit f to .saidtriangular pulse generator so as to develop a seriesof triangular pulses/of precise .timingI and duration, .and means fonapplyingthe triangular pulses thus developed toLthe input terminal .of :said delay line.

.16. The. combination :of claimt, in which the said .manually-adjustable vdelay unitv is responsive only to those portions of the pulses appearingatthe output terminal-ofsaidldelay line which aree-abovea. predetermined amplitude-level,

17; Thepcombination of -claim .5, further including..manuallyadjustab1e. control means located between':saidintegrating means f andu said-rectangularfwavefformmg circuit for varying :thewwi'dth 2l of the rectangular Waves produced thereby and hence the width of the triangular pulses developed by said triangular pulse generator.

WILSON P. BOOTHROYD.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Wheeler et al Aug. 20, 1940 Number Y Number Name Date 24,212,967 White Aug. 27, 1940 f 2,413,063 Miller Dec. 24, 1946 ,f 2,413,182 Hollingsworth et al. Dec. 24, 1946 2,436,808 Jacobsen et al Mar. 2, 1948 Y 2,446,106 Robertson July 27, 1948 2,485,124 Westcott Oct. 18, 1949 OTHER REFERENCES .Article entitled Design of Mercury Delay Lines, by T. K. Sharpless, Electronics of November 1947, pages 134-138. 

